Development of High Current Nb 3 Sn Rutherford Cables for NED and LARP

May 21, 2008WAMSDO, CERN

D.R. Dietderich, LBNL1

Development of High Current Nb3Sn Rutherford Cables for NED and LARP

D.R. Dietderich, A. Godeke, N.L. Liggins, and H.C. Higley

WAMSDO, May 2008



Outline

• Rutherford cables• Cabling objective:

– Damage free strand– Mechanically stable for winding a magnet

• Review cabling history for LBNL – Dipole D-20 (13.5/14.5T)– Recent rectangular cable fabrication for LBNL magnets

• RD-3 series (14.7 T)• HD-1 series (16 T)

• Cables for LARP Technology Quadrupoles (TQ)• Proto-type cables for Next European Dipole (NED)



60 Strand Machine for Fabricating Rutherford Cables



Typical Rutherford CableCable 961

Edge deformations are important



Good and bad cable edge deformation

• Bad • Good

Main difference is different width of the cable



Managing edge deformationProblem with Packing Factor

Two Cables have equal area but are NOT the same

17.4 mm x 1.400 mm = 24.4 mm2

17.0 mm x 1.435 mm = 24.4 mm20.8 mm strand diameter40 Strand cable

Cable Area = 24.40 mm2

87% Packing Factor

2 Cables: Same compaction orPacking Factor

0.4 is mm half a strand diameterThis difference can be fatal

Design for this strand configuration

at edge of cable

NOT this strand Configuration

t

w Bad

Good

Decoupling of Thickness & Widthas opposed to Packing Factor



Deformation Parameters t and w

• Thickness deformation t (~strain)t = (cable thickness/2x strand diameter) -1

• Width deformation w (~strain)w = (cable width – theoretical width)/(th. width)

Theoretical width =

PA = Cable pitch angle

(factor 0.72 d not included in plots in this presentation)



Rutherford Cable Parameter Space

Cable widerw larger

Cab

le th

inne

rt m

ore

nega

tive

No strand deformation at (0,0)2 wire diameters

(t=0)

Theoretical width (w=0)



Parameter space cables for D-20, RD-3, and HD-1

LBL Cable # 523 MJR-TWCA

LBL Cable # 522 IGC-Int. Tin

LBL Cable # 805ROxford-ORe

D-20 RD-3Internal Tin, MJR, and RRP

-0.40

-0.35

-0.30

-0.25

-0.20

-0.15

-0.10

-0.05

0.00

-0.04 -0.02 0.00 0.02 0.04 0.06 0.08

Width Parameter

Th

ickn

ess

Par

amet

er

D-20 Outer D-20 InnerRD-3 & HD-1LHC-HGQ

Abandoned

RD-3HD-1

Rect. D-20

Key. D-20

NbTiLHC-HGQ

Keystoned D20 cables had ~20% loss in Icand were more sensitive to transverse stress

D-20 is Cosine Theta Dipole (14.7T), RD-3 is Racetrack Dipole, and HD-1 is High Field Dipole (16T)



Internal Tin, MJR, and RRP

-0.40

-0.35

-0.30

-0.25

-0.20

-0.15

-0.10

-0.05

0.00

-0.04 -0.02 0.00 0.02 0.04 0.06 0.08

Width Parameter

Th

ickn

ess

Par

amet

er


Zones of interest from cables for D-20, RD-3, and HD-1

LBL Cable # 523 MJR-TWCA

LBL Cable # 522 IGC-Int. Tin

?Damaged Zone

Good Zone

LBL Cable # 805ROxford-ORe

MechanicallyUnstable

Abandoned

D-20 RD-3RD-3HD-1

Rect. D-20

Key. D-20

D-20 is Cosine Theta Dipole (14.7T), RD-3 is Racetrack Dipole, and HD-1 is High Field Dipole (16T)



Technology Quad (TQ) – Cable Specifications & Production

• Spec

• Made



TQ cable compared to past cables

Internal Tin, MJR, and RRP

-0.40

-0.35

-0.30

-0.25

-0.20

-0.15

-0.10

-0.05

0.00

-0.04 -0.02 0.00 0.02 0.04 0.06 0.08

Width Parameter

Thic

knes

s Pa

ram

eter


Abandoned Keystoned D-20 Cables

RD-3HD-1

Rect. D-20

Key. D-20

NbTiLHC-HGQ

TQ



Facet size as online probe

• Facet length (x) should be less than Pitch Length/strand (y) – Minor axis

Bad

Good



Thin edge of cables as online probe

939R

946R

Facets at cable edge SEM Images ofCross Section

Facets > Pitch length/strand

Facets < Pitch length/strand

Bad

Good2.0

2.2

2.4

2.6

2.8

3.0

3.2

3.4

928R-B 933R 939R 940R 946R 947RCable Number

Maj

or

Axi

s o

f fa

cet

and

PL

/27

(mm

)

Major Axis

PL /27 Strand



TQ cable widths after re-rolling• Do NOT re-roll cable to

a smaller width – Fabrication (first

rolling)– Anneal cable 200C for

4-6 h– Re-roll (second

rolling) – final cable

9.9

9.95

10

10.05

10.1

928R-B 933R 939R 940R 946R 947R

Cable No.

Cab

le W

idth

(mm

)

Cable Width First Roll

Cable Width

BAD

GOOD

Spec.

After cable 940R the processing was changed

From one set of rollsTo 2 sets of rolls,

One for the fabrication and one for re-rolling

~ 50 micrometer wider

Re-rolling after anneal is used to provide final shape

Process improvement



Summary of Critical and Stability Currents for TQ Cables

• All cables but 939R: – Reduced Jc(12T,4.2K) by about 0-3%

– Reduced stability current (Is) by ~10%

• Cable 939R (bad example with sheared sub-elements): – Reduced Jc (12T,4.2K) by about ~5% (Only)

– Reduced stability current (Is) by ~50% (RRR loss?)

• Concern – Past Jc measurements on cables with edge damage has shown them to be more sensitive to transverse stress.



NED Cable Parameters

• LBNL Cable-CALC– Should increase the width from 26 mm to 26.9 mm.

– Note: Removal of 1 strand is only 2.5% Ic reductionbut provides significantly more width margin



NED Cable Prototype Fabrication

• LBNL cabling machine was pushed to its limits due to the: – Large strand diameter

– High stiffness of the strand

• Higher tension on the strands should make the cabling process easier. – It should permit fabrication of cables with a lower pitch

angle (~16o)

– Plus reduce the gaps between strands



NED cable edge facet summaryFour short prototype cable sections made

• Facet/Pitch on the minor edge are similar• Section C has the smallest ratio• Section C has 4-8% Ic reduction (T. Boutboul, EUCAS-07 )

Facet Length mm

Pitch Length mm

Facet/PitchCable Pitch Length mm

965-A-Min 4.26 4.76 0.89 190.7965-A-Maj 4.11 4.83 0.85 193.1

965-C-Min 3.17 3.76 0.84 150.5965-C-Maj 3.45 3.76 0.92 150.5

965-D-Min 3.34 3.74 0.89 149.6965-D-Maj 3.65 3.79 0.96 151.5

965-E-Min 3.33 3.75 0.89 150.1965-E-Maj 3.57 3.77 0.95 150.9



NED spec and prototype

NED PrototypeSpec



Strand deformation inside a cable

• Dimples at strand cross over points (box) – Deformation not uniform

along a strand – Making cables thinner has

shown no significant impact on performance

– Perhaps cables can be made thinner

• Strand deformation as it goes from the top of cable to bottom (oval) – Limits cable performance

• Need 3D modeling to understand strand deformation at the cable edge

Cable 784R



Modeling 2D and 3D

3D Modeling of Strand2D Strand Modeling

• S. Farinon, Presented at CHATS-AS 2006

Marco La China



Summary

• The facet size on the edge of the cable provides a direct measure of the amount of strand deformation. – Indicates the amount of sub-element distortion inside the strand.

• This work shows that a nearly damage-free mechanically-stable cable can be produced from: – MJR and RRP strands with reduction of only 0-3% Jc (12T,4.2K). – PIT strand with reduction of 4-8% Jc (12, 4.2K)

• Cabling damage (i.e. sheared sub-elements) had minimal effect on Jc but it has a significant impact on strand stability.– The stability current (Is) drops by ~50% in a strand with only a ~5% drop in

Jc at 12T and 4.2K

Development of High Current Nb 3 Sn Rutherford Cables for NED and LARP

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